Manufacturing method for diffuser

ABSTRACT

A manufacturing method for a diffuser comprises a first process of forming a first molded component, by gradually forging a cylindrical solid material having fiber flow extending in an axial direction from an axial direction thereof, the first molded component including a flange section having a central hole section, and a bottomed cylindrical section having a communication hole leading to one end, in the axial direction, of the flange, and communicating with the hole section, and having fiber flow that is flowing substantially in the axial direction without being cut, and a second process of forming a second molded component, by split molding a peripheral groove using split dies at the outer periphery of the bottomed cylindrical section of the first molded component, including a flange having a central hole section, and a bottomed cylindrical section having a communication hole leading to one end, in the axial direction, of the flange, and communicating with the hole section, and having the peripheral groove formed without cutting fiber flow. The embodiment provides a manufacturing method for a diffuser that can be produced with high yield and at low cost, while doing away with locations where fiber flow is cut and that has no gas leakage.

RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2010-206091, filed on Aug. 27, 2010, the entire content of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a manufacturing method for a diffuser of an inflator for an airbag used to expand an airbag of a vehicle.

BACKGROUND ART

Conventionally, a diffuser such as shown in the cross sectional diagram of FIG. 8 has been used as a diffuser of an inflator for this type of air bag. Fiber flow is an important factor, and so in the cross section hatching has been omitted.

As shown in FIG. 8, this diffuser 6A has a flange 61 with a central hole section 61 a and an outer engagement section 61 b, and a bottomed cylindrical section 63 having a communicating hole 63 a that leads to one end, in an axial direction, of the flange 61 and communicates with the hole section 61 a, with a peripheral groove 63 b formed on an outer peripheral section of the bottomed cylindrical section 63, and a plurality of exhaust ports 64 b that communicate with an airbag extending radially to the bottom section of the communication hole 63 a. An outer end surface of the flange 61 is then attached to an opening section of a high pressure gas container 10 by welding, while an airbag 11 is engaged in the outer peripheral portion of the bottomed cylindrical section 63, and attached by mechanical fastening by means of the peripheral groove 63 b.

As a method for manufacturing the above described diffuser, first, in order to increase yield and reduce cost, using cylindrical solid material (wire rod cut to a specified length) extending in the axial direction of fiber flow, a first molded component 3A comprising as shown in FIG. 9 a flange 31 having a central hole section 31 a and a bottomed cylindrical section 33 that leads to one end, in the axial direction, of the flange 31 and has a communication hole 33 a communicating with the central hole section 31 a, is formed by gradually forging this cylindrical solid material in the axial direction using a former or press, and then a second intermediate molded component 4A is formed by forming a peripheral groove 43 b by a cutting operation on the outer periphery of the bottomed cylindrical section 33 of the first molded component 3A, as shown in FIG. 10. After that, as shown in FIG. 8, a cutting operation of an outer end engagement section 61 b for engaging with an outer end surface of a flange 41 of the second molded component 4A, and a cutting operation of a small diameter communication hole 64 a that communicates with a bottom section of the communication hole 43 a of the bottomed cylindrical section 43 and a plurality of expulsion holes 64 b that communicate with the small diameter communication hole 64 a, are carried out.

However, according to the above described manufacturing method for a diffuser, while it is possible on the one hand to improve yield and reduce cost, when forming the outer groove 43 b on the outer periphery of the bottomed cylindrical section 33 of the first molded component 3, formation of the peripheral groove 43 b is carried out using a cutting operation, which means that fiber flow extending in the axial direction is cut midway, as shown in FIG. 10. As a result, as shown in FIG. 8, when having attached the diffuser 6A to the high-pressure gas container 10 by welding, there is a problem that high-pressure gas leaks out from the peripheral groove section 63 b where fiber flow is cut at a very small proportion of one in several ten-thousands components.

The cause of this gas leakage is a phenomenon where very small amounts of high pressure gas escape with an extremely low probability along fiber flow and non-ferrous inclusions within the steel formed with strengthening processing by cold forging of the material (steel). As a result, leakage of a very small amount of high pressure gas from sections of the peripheral groove 63 b where the fiber flow has bee cut occurs at a very small proportion, e.g., one of ten-thousands of diffuser due to the above described phenomenon. With respect to this problem, after manufacture of the diffuser total inspection of the diffuser to be used is carried out to see whether or not gas leaks have occurred in sections where the fiber flow of the peripheral groove 63 b has been cut, and only those in which gas leaks have not occurred are used. As a result, inspection is time consuming and this in turn pushes up costs. The occurrence of fiber flow arises naturally with cold forging, and non-ferrous inclusions in the material have been considerably improved at the time of steel making at a steel producer, but the actual situation is that they have not been completely eliminated.

SUMMARY OF THE INVENTION

The present invention therefore provides a manufacturing method for a diffuser that can be produced with high yield and at low cost, while doing away with locations where fiber flow is cut and that has no gas leakage.

An invention of a first aspect of this application is a manufacturing method for a diffuser including a flange with a central hole section and an outer engagement section, and a bottomed cylindrical section having a communicating hole that leads to one end, in an axial direction, of the flange and communicates with the hole section, with a peripheral groove formed on an outer peripheral section of the bottomed cylindrical section, and a plurality of expulsion ports that communicate with an airbag extending radially to the bottom section of the communication hole, comprising:

a first process of forming a first molded component using a cylindrical solid material having fiber flow extending in an axial direction in order to prevent material loss, and by gradually forging a cylindrical solid material from an axial direction thereof, the first molded component including a flange section having a central hole section, and a bottomed cylindrical section having a communication hole leading to one end, in the axial direction, of the flange, and communicating with the hole section, and having fiber flow that is not cut and flowing substantially in the axial direction; and

-   -   a second process of forming a second molded component by split         molding a peripheral groove using split dies at the outer         periphery of the bottomed cylindrical section of the first         molded component, the second molded component including a flange         having a central hole section and a bottomed cylindrical section         having a communication hole leading to one end, in the axial         direction, of the flange, and communicating with the hole         section, and having the peripheral groove formed without cutting         fiber flow.

An invention of a second aspect of this application is a manufacturing method for a diffuser including a flange with a central hole section and an outer engagement section, and a bottomed cylindrical section having a communicating hole that leads to one end, in an axial direction, of the flange and communicates with the hole section, with a peripheral groove formed on an outer peripheral section of the bottomed cylindrical section, and a plurality of expulsion ports that communicate with an airbag extending radially to the bottom section of the communication hole, comprising:

a advance process of forming an intermediate component, formed by gradually forging a cylindrical solid material that has fiber flow extending in an axial direction using a multistage former or press, the intermediate component including a flange and a cylindrical section that extends axially outward from a central section at one end, in the axial direction, of the flange, via a step section and having a smaller diameter than the step section, and having fiber flow flowing in substantially the axial direction without being cut;

a first process of forming a first molded component by press forming the intermediate component from the axial direction using a press unit, the first molded component including a flange having a central hole section, and a bottomed cylindrical section of smaller diameter than the outer diameter of a step section, the first molded component having a communication hole that extends axially outwards from a central section of one end of the flange in the axial direction and communicates with the hole section, with fiber flow flowing in a substantially axial direction without being cut; and

-   -   a second process of forming a second molded component by a split         mold upset process so as to extend only tip end of the bottomed         cylindrical section in a state where a boundary division of the         step section and the bottomed cylindrical component of the first         molded component is restrained by split dies, the second molded         component including a flange having a central hole section, and         a bottomed cylindrical section extending axially outward at the         same diameter as the outer diameter of the step section from the         center section of one end, in the axial direction, of the         flange, and having a peripheral groove at the middle in the         axial length of the bottomed cylindrical section, the peripheral         groove being formed without cutting the fiber flow.

According to the manufacturing method for a diffuser of the first aspect of this application, it is possible to gradually forge shape a solid cylindrical material that has fiber flow extending in an axial direction from the axial direction thereof, and so it is possible to achieve high yield and low cost, and moreover in the second process, since the second molded component has the peripheral groove formed on an outer periphery of the bottomed cylindrical section without cutting the fiber flow by split forging a peripheral groove using the split dies on an outer periphery of the bottomed cylinder, fiber flow is not cut accompanying peripheral groove formation, and it is possible to prevent gas leaking from locations where the peripheral groove is formed when attaching a high pressure gas container to an outer surface of the flange In this way, after manufacture of a diffuser it is not necessary to test whether or not gas leaks occur at the peripheral groove section, meaning it is possible to omit the time taken for testing, and also, since it is also possible to guarantee the gas leak free with the manufacturing process it is safe to use, and it is possible to reduce cost.

Also, according to the manufacturing method for a diffuser of the second aspect of this application, first, as the advance process, an intermediate component, including a flange and a cylindrical section of a smaller diameter than a step section that extends axially outward from one end central section in the axial direction, of the flange, via the step section, and having fiber flow flowing in substantially the axial direction without being cut, is formed by gradually forging a cylindrical solid material that has fiber flow extending in an axial direction, from the axial direction, using a multistage former or press, next, in the first process, a first molded component is formed by press forming the intermediate component from the axial direction using a press unit, the first molded component including a flange having a central hole section, and a bottomed cylindrical section of smaller diameter than the outer diameter of a step section having a communication hole that extends axially outwards from a central section of one end of the flange in the axial direction and communicates with the hole section, and having fiber flow axially flowing without being cut, and after that, a second molded component is formed by a split mold upset process so as to expand only tip end of the bottomed cylindrical section in a state where a boundary division of the step section and the bottomed cylindrical component of the first molded component is restrained by the split dies, the second molded component including a flange having a central hole section, and a bottomed cylindrical section having a peripheral groove extending axially outward at the same diameter as the outer diameter of the step section from the center section of one end, in the axial direction, of the flange, and at the middle of the axial length of the outer peripheral of the bottomed cylindrical section, and the peripheral groove is formed without cutting fiber flow, which means that similarly to the above described first aspect, there are no places where fiber flow of the peripheral groove section is cut, and it is possible to completely prevent gas leaking at places where the peripheral groove is formed, when having attached a high pressure gas container to an outer surface of the flange. In this way, after manufacture of a diffuser it is not necessary to test whether or not gas leaks occur at the peripheral groove section, meaning it is possible to omit the time and effort for testing, and surely guarantee the gas leak free with the manufacturing process, and it is possible to reduce cost. Further, the intermediate component is forge shaped inexpensively using a former, the first molded component is formed to high precision using a press unit, and the second molded component can be manufactured to high precision by carrying out a split mold upset process using the split dies, and it is possible to proactively reduce costs.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further described with reference to the accompanying drawings wherein like reference numerals refer to like parts in the several views, and wherein:

FIG. 1 is a cross sectional drawing of a blank for a diffuser manufacturing method of the present invention;

FIG. 2 is a cross sectional drawing of an intermediate molded component in which a blank is formed by cold forging;

FIG. 3 is a cross sectional drawing of a molded component with a hole section formed in the process after that shown in FIG. 2;

FIG. 4 is a cross sectional drawing showing a molded component that has had a peripheral groove upset molded with a split mold in the process after FIG. 3;

FIG. 5 is a cross sectional drawing of a molded component that has been subjected to cutting process in the process after that shown in FIG. 4;

FIG. 6 is a cross sectional drawing of a final molded component that has had expulsion holes cut in the process after that shown in FIG. 5;

FIG. 7 is an outline explanatory drawing showing a usage state of the diffuser;

FIG. 8 is a drawing for describing a diffuser manufacturing method of related art;

FIG. 9 is a cross sectional drawing of a molded component before forming a peripheral groove in the diffuser manufacturing method of the related art; and

FIG. 10 is a cross sectional drawing of a molded component that has had a peripheral groove formed by cutting in the diffuser manufacturing method of the related art.

DETAILED DESCRIPTION OF THE EMBODIMENTS

A diffuser manufacturing method of the present invention will be described in the following based on the drawings.

FIG. 1 to FIG. 7 respectively show formation explanatory drawings for one embodiment using the diffuser manufacturing method of the present invention, and a molded component at each step is shown in a front elevation or a cross sectional view. Fiber flow is an important factor the embodiment, and so in the case of cross sectional views hatching has been omitted.

FIG. 1 shows a cylindrical solid material 1 having fiber flow extending in an axial direction. This solid material 1 may be a blank formed by previously cutting a wire to specified dimensions, or may be a material formed by cutting sequentially supplied wire using a cutting machine at the time of forging using a former. Here fiber flow is flowing in the axial direction, as shown in FIG. 1.

As shown in FIG. 2, the solid material 1 is gradually forge shaped from the axial direction thereof using a die and a punch, at each forging station of a multistage former, to form a solid intermediate component 2 that comprises a flange 21 having a circular outer periphery, a cylindrical section 23 extending axially outward via a step section 22 from a central section at one end in the axial direction of the flange 21, and a small diameter projecting section 24. Here, fiber flow of the intermediate molded component 2 is flowing substantially in the axial direction, without being cut, as shown in FIG. 2.

Next, as shown in FIG. 3, the solid intermediate molded component 2 that was forge shaped by the former is subjected to press forming from an axial direction of the intermediate molded component 2 using an upper mold and a lower mold at a first press station of a vertical press unit (not shown), to form a high precision first molded component 3 comprising a flange 31 having a central hole section 31 a, a bottomed cylindrical section 33 that extends axially outward via a step section 32 from a center section at one end, in the axial direction, of the flange 31 and has a communication hole 33 a leading to the hole 31 a of the flange 31, and a small diameter projecting section 34. Here, fiber flow of the first molded component 3 is flowing substantially in the axial direction, without being cut, as shown in FIG. 3.

In FIG. 4, the first molded component 3 is subjected to forging processing so as to expand only tip end of the bottomed cylindrical section 33 in a second press station, using the upper mold and the lower mold provided with the split dies of a vertical press unit, from an axial direction of the first molded component 3, with a boundary portion of the step section 32 and the bottomed cylindrical section 33 being restrained by the split dies. In this way, a high precision second molded component 4 comprising the flange 41 having the central hole section 41 a as shown in FIG. 4, the bottomed cylindrical section 43 (also including the step section 32) extending axially outwards from the central hole section of one end in the axial direction of the flange 41 at the same diameter as the outer diameter of the step section 32, and being provided with the peripheral groove 41 b at the middle of the axial length of the outer periphery of the bottomed cylinder section 33, and having a communication hole 43 a leading to the central hole section 41 a of the flange 41, and the small diameter projecting section 44, is formed. Here, fiber flow of the second molded component 4 is flowing substantially in the axial direction, without being cut, as shown in FIG. 4.

After that, as shown in FIG. 5, the second molded component is shaped by cutting out an engagement section 51 b for attachment of a blocking plate etc. of a gas canister around a central hole section 51 b of an outer surface of the flange 41 using a first cutting station of a cutting unit (not shown), and a third molded component 5 is formed by cutting out a small diameter communication hole 54 a extending into the small diameter projecting section 54 from the bottom section of the communicating hole 53 a of the bottomed cylindrical section 53. In FIG. 5, blackened sections are cutting locations, and reference numeral 7 indicates a holding section for when cutting the second molded component 4.

Further, as shown in FIG. 6, a diffuser 6 is formed as a finished product by cutting a plurality of expulsion holes 64 b . . . 64 b extending in a radial direction close to the bottom section of the small diameter communication hole 54 a of the small diameter projecting section 54 of the third molded component 5. In FIG. 6, blackened sections are cutting locations, and reference numerals 8 and 9 indicate holding sections for when cutting the second molded component 4.

The diffuser 6 that has been formed in this way then has an outer end surface of the flange 61 attached to an opening section of a high pressure gas container 10 by welding, as shown in FIG. 7, while an airbag 11 is engaged in the outer peripheral portion of the bottomed cylindrical section 63, and attached by mechanical fastening by means of the peripheral groove 63 a.

According to the diffuser 6 manufactured as descried above, there are no places where fiber flow of the portion of the peripheral groove 63 b is cut, and it is possible to prevent gas leaking from portions of the peripheral groove 63 a, when attaching a high pressure gas container 10 to an outer surface of the flange. In this way, after manufacture of a diffuser 6 it is not necessary to test whether or not gas leaks occur at parts of the peripheral groove 64 b, meaning that it is possible to omit the time and effort for testing, and it is possible to reduce cost. Further, with the above described embodiment, first the intermediate second molded component is inexpensively mass produced by forging using a multi-stage former, then the first and second molded components 3, 4 are press molded to high precision using a vertical press unit, and after that the third molded component 5 and final molded component 6 are cut using a cutting unit, which means that it is possible to finally manufacture with high precision by combining these steps, and it is also possible to proactively achieve cost reduction.

As described above, the multi-stage former, the vertical press unit and the cutting unit may be combined, but it is also possible, for example, to continuously carry out using only a press unit by carrying out using press forming of the intermediate molded component 2.

Although the present invention has been fully described by way of examples with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. Therefore, unless such changes and modifications depart from the spirit and the scope of the present invention, they should be construed as being included therein. 

What is claimed is:
 1. A manufacturing method for a diffuser comprising a flange with a central hole section and an outer engagement section, and a bottomed cylindrical section having a communicating hole that leads to one end, in an axial direction, of the flange and communicates with the hole section, with a peripheral groove formed on an outer peripheral section of the bottomed cylindrical section, and a plurality of expulsion ports that communicate with an airbag extending radially to the bottom section of the communication hole, comprising: a first process of forming a first molded component, by gradually forging a cylindrical solid material from an axial direction thereof using the cylindrical solid material having fiber flow extending in an axial direction in order to prevent material loss, the first molded component including a flange section having a central hole section, and a bottomed cylindrical section having a communication hole leading to one end, in the axial direction, of the flange, and communicating with the hole section, and having fiber flow that is not cut and flowing substantially in the axial direction; and a second process of forming a second molded component, by split molding a peripheral groove using split dies at the outer periphery of the bottomed cylindrical section of the first molded component, the second molded component including a flange having a central hole section, and a bottomed cylindrical section having a communication hole leading to one end, in the axial direction, of the flange, and communicating with the hole section, and having the peripheral groove formed without cutting fiber flow.
 2. A manufacturing method for a diffuser comprising a flange with a central hole section and an outer engagement hole section, and a bottomed cylindrical section having a communicating hole that leads to one end, in an axial direction, of the flange and communicates with the hole section, with a peripheral groove formed on an outer peripheral section of the bottomed cylindrical section, and a plurality of expulsion ports that communicate with an airbag extending radially to the bottom section of the communication hole, comprising: an advance process of forming an intermediate molded component, by gradually forging a cylindrical solid material that has fiber flow extending in an axial direction using a multistage former or press, the intermediate molded component including a flange, and a cylindrical section of a smaller diameter than a step section that extends axially outward from a central section at one end, in the axial direction, of the flange, via the step section, and having fiber flow flowing in substantially the axial direction without being cut; a first process of forming a first molded component by press forming the intermediate component from the axial direction using a press unit, the first molded component comprising a flange having a central hole section, and a bottomed cylindrical section of smaller diameter than the outer diameter of a step section having a communication hole that extends axially outwards from a central section of one end of the flange in the axial direction and communicates with the hole section, with fiber flow flowing in a substantially axial direction without being cut; and a second process of forming a second molded component by a split mold upset process so as to expand only a tip end of the bottomed cylindrical section in a state where a boundary division of the step section and the bottomed cylindrical section of the first molded component is restrained by split dies, the second molded component including a flange having a central hole section, and a bottomed cylindrical section having a peripheral groove and extending axially outward at the same diameter as the outer diameter of the step section from the center section of one end, in the axial direction, of the flange, at a middle of the axial length of the outer periphery of the bottomed cylindrical section, and having the peripheral groove formed without cutting fiber flow. 